1. Field of the Invention
This invention relates to housings for disks of filter material.
2. Description Relative to the Prior Art
U.S. Pat. No. 2,808,937, issued to O'Meara on Oct. 8, 1957, describes a filter housing which includes two dome-shaped housing parts with a resilient O-ring disposed between annular flanges at their mating free edges. Means are provided for forcing the housing parts together, thereby compressing the O-ring. A disk of filter material is disposed with its periphery between the O-ring and the flange of one housing part, before the housing parts are brought together and forced together. Such an arrangement has the disadvantage that material being filtered can escape to the exterior of the housing by passing laterally through the flexible fibrous filter material. If the filter disk is very carelessly installed, there is the possibility that at a portion of its periphery there is a gap between the periphery and the O-ring, allowing material to be filtered passing directly to the output chamber of the housing where it mixes with filtrate.
U.S. Pat. No. 3,085,689, issued to Hering et al on Apr. 16, 1963, describes what may, in some respects, be termed an improvement over the housing described in the O'Meara patent. The Hering housing includes a resilient element which is compressed between first and second housing parts. The resilient element seats on one housing part and has two rings of contact with the other housing part. At the inner ring of contact, the periphery of the filter disk is compressed between the resilient element and the other housing part. It is intended that the filter disk not extend into the other ring of contact. However, if the filter disk is faultily installed, as could occur with even the most conscientious person when working in the dark, as must often occur in the photographic industry, the filter disk could again provide a path for material being filtered, to the exterior of the housing. Again faulty installation could create a path bypassing the filter disk and allowing unfiltered material to mix with filtrate.
Obviously both the escape of material to the exterior of the housing and the presence of material intended to be filtered out, in the filtrate are both very undesirable occurrences. Likewise, if the interior of the filter housing is at sub-ambient pressure, atmosphere could be introduced into the filtrate through the filter disk if it extends past the seal.
It is an object of the present invention to overcome the problems of the prior art and provide a superior filter housing which provides aids to prevent faulty insertion of a filter disk and provides a seal preventing lateral leakage through the filter disk reaching the exterior of the housing.